Reamer with radial relief

ABSTRACT

A finish reamer adapted to finish ream a phosphor bronze valve guide insert is disclosed. The reamer includes a body section having a plurality of spiral flutes formed therein. The flutes define a plurality of cutting blades. Each cutting blade has an axially extending radial relief formed therein.

BACKGROUND OF THE INVENTION

The present invention relates to cutting tools and more particularly tofinish reamers.

In a wide variety of manufacturing and repair or reconditioningprocesses, it is necessary to accurately cut a hole or bore to apredetermined inner diameter. For example, such a cutting operation isperformed in some of the various methods which have heretofore beendeveloped for rebuilding of internal combustion engine valve guides.After extensive use, the valve guides of an internal combustion enginewill wear presenting excessive clearance between the valve guide and thevalve stem. This excessive clearance may have an adverse effect on valvetrain operation and also increases undesirable emissions from theinternal combustion engine.

The various methods heretofore proposed have included lining or reliningof the worn valve guides with generally cylindrical inserts. In atypical rebuilding process, a worn valve guide is bored out to receivethe insert which is press fit or forced into the bored out valve guidepassageway. The insert is finish reamed so that the internal diameter isaccurately cut and dimensioned with respect to the stem of the valvewhich reciprocates within the rebuilt valve guide.

Inserts of various materials, such as cast iron, thin wall, siliconbronze-aluminum and phosphor bronze, have been employed in suchrebuilding methods. Cast iron inserts present certain inherent problemsprimarily related to cost, rate of wear and heat transfercharacteristics. In order to overcome these problems, different forms ofbronze, and particularly phosphor bronze, inserts have been developed.The phosphor bronze material is harder than cast iron and siliconbronze-aluminum. Phosphor bronze inserts provide increased wearcharacteristics and heat transfer properties. Examples of phosphorbronze inserts may be found in U.S. Pat. No. 3,828,415 entitled METHODAND APPARATUS FOR REBUILDING VALVE GUIDES and issued on Aug. 13, 1974,to James A. Kammeraad and Donald J. Kammeraad and U.S. Pat. No.4,103,662 entitled INSERT FOR REBUILDING VALVE GUIDES and issued on Aug.1, 1978, to James A. Kammeraad.

One of the inserts disclosed in U.S. Pat. No. 3,828,415 is a thin walltubular member stamped from a blank of phosphor bronze and progressivelyformed into a tubular shape leaving a longitudinal slit. The insert isforced into a reamed valve guide by means of an adapter. The outerdiameter of the insert is greater than the reamed valve guide so thatthe insert is radially compressed when it is forced into the reamedvalve guide. The insert is then trimmed so that it is flush with thevalve guide. The inner surface of the insert may then be knurled to flowthe metal and seal off the passage through the slit. Finally, the valveguide is finish reamed to a predetermined diameter as required for theparticular size of valve stem. The tubular insert has a wall thicknessin the range of 10 to 25 thousandths of an inch and is preferably in therange of 15 to 20 thousandths of an inch.

An insert as disclosed in U.S. Pat. No. 4,103,662 includes an innersleeve or tube of spring-tempered phosphor bronze and an outer carriersleeve or tube of steel or aluminum. The separate formation of the innerand outer sleeves allows precise control of wall thicknesses, diametersand concentricities.

With each type of valve insert disclosed in the aforementioned patents,the finish reaming step is typically, although not always, performedwith a high speed reamer. Reamers are fabricated in a plurality ofgraduated, standard diameter sizes to accommodate the different sizes ofvalve guides. The reamers each include a plurality of flutes whichdefine cutting blades. The flutes may be straight or spiral cut.Typically, a spiral flute reamer is used since it provides a betterfinish and a smoother cutting of the insert passageway than a straightcut reamer.

Conventional reamer blades each include a rake face, a cutting edge, aland having a margin and a relief, and a trailing portion. The land maybe circular or convex and is typically relieved to avoid interferenceand rubbing with the work piece. Such reamers may be manufactured fromhigh speed steel and a fluting cutter is employed to cut the flutes intothe reamer blank. Further, the reamer portion may be back tapered toprevent binding of the reamer within the bore which is being enlargedand finished. An example of a prior reamer may be found in U.S. Pat. No.2,940,342 entitled REAMERS and issued on June 14, 1969, to Lavallee.

The heretofore available finish reamers employed to finish thepassageways of phosphor bronze valve inserts have suffered from variousproblems primarily related to wearability. The prior reamers after fiveor six reaming operations are no longer able to hold their size. Use ofthe tool for additional reaming operations results in unacceptabledimensioning and finishing of the phosphor bronze valve guide insert.

SUMMARY OF THE INVENTION

A need exits for an improved finish reamer providing increased toollife, increased ease of cutting and which will hold the hole size longerthan the reamers heretofore available and which is adapted to cut hardmaterials such as phosphor bronze. Essentially, the finish reamer inaccordance with the present invention includes a body section havingformed therein a plurality of flutes with each flute defining a cuttingblade. Each blade includes a rake face, a cutting edge and a radiallyouter clearance face or margin. The margin along a portion thereof isformed with a radial relief opening through the rake face anddimensioned so as not to contact the work piece during reamer operation.

It is believed that the primary cause of the poor tool life heretoforeexperienced when finish reaming hard materials such as phosphor bronzehas been the heat generated in the reamer and in the insert during thereaming operation. It is further believed that the reamer in accordancewith the present invention possesses significantly increased tool lifedue to better heat dissipation which is the result of formation of aradial relief in the cutting blades.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side elevational view of a finish reamer in accordance withthe present invention;

FIG. 2 is a right end elevational view of the reamer of FIG. 1;

FIG. 3 is a fragmentary, sectional view taken generally along lineIII--III of FIG. 1; and

FIG. 4 is a greatly enlarged pictorial view of a portion of the reamerof FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

A finish reamer in accordance with the present invention is illustratedin FIG. 1 and generally designated 10. The finish reamer 10 includes anelongated member having a pilot section 12, a finish reamer or bodysection 14 and a cylindrical shank section 16. The cylindrical shanksection terminates in a conventional tang 18. The tang 18 is chuckedinto a suitable power tool in a conventional fashion.

The pilot section 12 includes a conical or chamfered leading end 20, acylindrical portion 22 and a fluted portion 24. Portion 24 includes aplurality of flutes 26. Flutes 26 are formed in the reamer blank in aconventional fashion employing a fluting cutter which removes materialfrom the blank. Each of the flutes 26 defines a cutting blade 28.

The finish reamer or body section 14 similarly includes a plurality offlutes 30. Flutes 30 are a continuation of flutes 26 formed in pilotsection 12 of the tool. Flutes 30 define finish reamer section cuttingblades 32. In the preferred embodiment, six flutes are formed in thetool 10 and they assume a righthand helix or spiral angle of ten (10)degrees with respect to the longitudinal centerline of the tool.

Blades 28 of the pilot section 12 are tapered. Blades 28 and thecylindrical portion 22 pilot or align the tool 10 within the bore whichis being finished. Each cutting blade 28 includes a land 31 which is afull circular land and has no relief. As seen in FIG. 3, each of theblades 32 of the reaming or body section 14 includes a rounded leadingedge 35, a rake face 34, a land 36 which includes a margin 38 and a heel40, and a trailing surface 42. Heel 40 of each land 36 is angledrelative to a line extending tangentially from the margin 38 at a reliefangle designated a (FIG. 3). In the preferred embodiment, the reliefangle a is approximately ten (10) degrees. Rake face 34 is angled fromthe vertical, as seen in FIG. 3, at a rake angle designated b. In thepreferred embodiment, rake angle b is approximately two (2) degrees. Theintersection between the rake face 34 and the margin 38 defines acutting edge 44. Rake face 34 and margin 36 of the finish reamer section14 are formed in a conventional fashion by conventional processes.

As best seen in FIG. 4, each blade 28 terminates in an angled surface50. The leading edge of finish reamer section 14 is defined by a chamfer52 cut into each blade 30. In the preferred embodiment, chamfer 52 has achamfer angle designated c in FIG. 4 of approximatel thirty (30)degrees. Further, as seen in FIG. 4, each chamfer 52 is ground with achamfer relief angle relative to a line perpendicular to thelongitudinal centerline of the tool and generally designated d ofapproximately twelve (12) degrees.

It is presently preferred that the cylindrical portion 22 of the pilotsection have a constant diameter designated d₁ in FIG. 1. Tool 10 tapersto a point of maximum diameter from the beginning or leading edge of theblades 28 in the pilot section to a point spaced rearwardly from thechamfers 52 on the finish reaming section 14. The point of maximumdiameter is designated d₂ in FIG. 1. The maximum diameter d₂ is thefinish diameter of the bore to be reamed. The finish reamer section 14has a back taper from the point of maximum diameter to the shank 16. Theshank 16 is formed with a constant diameter designated d₃ in FIG. 1.Each land 36 has an overall width designated W₁ and each circular marginportion 38 has a width designated W₂ in FIG. 3. Further, the diameterbetween opposed leading edges 61 of chamfers 52 is designated d₄ in FIG.1.

In accordance with the present invention, each of the cutting blades 32of the reamer section 14 has ground therein an axially extending, radialrelief 60. Each radial relief 60 extends transversely across the entirewidth of land 36 and opens through rake face 34. Each radial relief isspaced a distance l₁ from a trailing edge 63 of chamfer 52. Further,each radial relief 60 has a length l₂, rounded leading and trailing endsor edges having a radius R₁ and a flat section or portion 67. Eachrelief 60 has a depth or height designated h₁ in FIG. 4. Reliefs 60 havea length along the blade which is greater than the width of the land.Radial reliefs 60 are ground into the lands 36 of the cutting blades 32at points spaced rearwardly from the point of maximum diameter of thetool and the trailing edge of chamfer 52. Further, the depth or heighth₁ of each relief is such that the tool in the area of the relief doesnot engage the work surface.

The length dimension of each relief 60 and the positioning on thecutting blade is such that a terminal edge 65 is located rearwardly ofthe point of maximum diameter d₂ along the back taper of the tool. Thecutting blades continue rearwardly of the radial relief. The positioningof the relief prevents the occurrence of a secondary spiral being cut inthe work piece. The portions of each cutting blade rearwardly of theradial relief assist in piloting the tool and improve the surfacefinish. If terminal edge 65 were not along the back taper, anothercutting edge would be formed giving unacceptable results. The cuttingblade portions rearwardly of the radial reliefs are necessary for a goodfinish when the tool is used to ream the rather long valve insert bores.

It is believed that the relief significantly increases heat dissipationand significantly reduces the heat generated during operation of thetool. Increased heat dissipation increases the efficiency and ease offinish cutting of the bore and cutting pressures are reduced. Also, thetool in accordance with the present invention has exhibited asignificant increase in tool life. For example, a prior reamer used tofinish phosphor bronze valve inserts provided acceptable finishing foronly five or six reaming operations. In contrast, a tool in accordancewith the present invention has been employed to finish ream phosphorbronze valve guide inserts for two hundred reaming operations. Thepresent invention, therefore, has permitted a significant decrease inthe cost of performing finish reaming operations due primarily toincreased tool life and a corresponding decrease in the cost of valveguide rebuilding.

The prior approach to achieving increased tool life has generally beento increase the width W₂ of margin portion 38. This approach has beenused particularly with tools designed to ream cast iron. In starkcontrast, the tool in accordance with the present invention includes arelief angle which would be considered radical and a reduced marginwidth than heretofore considered normal practice. The rake angle a, thedimensions W₂ and W₁, the positioning and dimensioning of the radialreliefs 60, co-act to increase heat dissipation and eliminate holedimension changes due to expansion of the tool and the work piece duringoperation from the heat generated. The cutting blade portions rearwardlyof the radial reliefs are able to accurately align and surface finishsince the change in tool and work piece dimensions due to heat areeffectively stopped. The reduced margin width reduces friction therebyreducing heat generation and heating of the tool and the work piece. Theproblems heretofore experienced, it is believed, were primarly caused bythe length of the bore of the insert and the length of the ream. Giventhe length of the ream the degree of accuracy of prior tools could notbe maintained for an acceptable number of operations.

Reamers in accordance with the present invention are fabricated in aplurality of graduated diameter sizes to finish ream the various sizesof valve guide inserts presently available. Presently existingembodiments of the finish reamer have a pilot section 12 with an overalllongitudinal dimension of 1.00 inch, a finish reamer section 14 with anoverall longitudinal dimension of 1.87 inches and an overall length ofapproximately 7.00 inches. The conical portion or surface 20 of pilotsection 12 is chamfered or beveled at an angle of thirty (30) degreesfrom vertical.

Cylindrical portion 22 in such presently existing embodiments has adiameter d₁ of approximately 0.295 inches, dimension d₄ is approximately0.248 inches and the maximum diameter d₂ of the finish reamer portion isapproximately 0.310 inches. This maximum diameter occurs a point spaced1/8 of an inch from a trailing edge 63 of chamfer surface 52. It ispreferred that theback taper runs towards shank portion 16 the fullaxial length of cutting blades 32. The preferred back taper is equal to0.0008 inches per inch. The leading edge 62 of each radial relief 60 ispositioned at a distance l₁ of approximately 0.375 inches along thecutting blade 32. The overall length l₂ of the radial relief isapproximately 0.5 inches and the depth or height h₁ is approximately0.007 inches. The radius R₁ is approximately 0.060 inches and thediameter d₃ of the shank portion 16 is approximately 0.305 inches. Theoverall circular land width W₁ of each cutting blade is approximately0.040 inches and the width W₂ of the margin 38 is within the range of0.011 to 0.016 inches. In other words, the width of the margin is withinthe range of 27.5 percent to 40 percent of the overall width of theland. The ratio of the length l₂ of the relief along the cutting bladeto the longitudinal dimension of the body portion or reamer section 14is approximately 0.267. The ratio of the depth of the radial relief 60to the overall length l₂ of the radial relief is approximately 0.014.The distance l₂ is approximately 75 percent of the length dimension ofthe radial relief along the blade. It is presently preferred that thetool 10 be fabricated from a high speed steel and heat treated to anRC-63 minimum hardness. Further, it is preferred that the shank bepolished after heat treating to insure that there are no burrs or sharpedges on the shank. Other materials, such as carbon steel or carbide,could be used.

In the method of rebuilding a valve guide employing the tool inaccordance with the present invention, tubular bronze inserts of thetype illustrated in the aforementioned U.S. patents are positionedwithin a bored valve guide. The reamer 10 is then chucked to a suitablepower tool, positioned within the tubular insert and rotated to finishream the insert to the predetermined inner diameter. To the extentnecessary, the disclosures of the aforementioned U.S. Pat. Nos.3,828,415 and 4,103,662 are hereby incorporated by reference.

In view of the foregoing description, it should be readily apparent tothose of ordinary skill in the art that the unique finish reamer inaccordance with the present invention possesses significant advantageswhen compared to the prior high speed finish reamers. The reamer inaccordance with the present invention significantly increased tool life,an increase in ease of use, possesses the ability to hold the properhole size longer and results in significantly reduced costs than haveheretofore been obtainable.

Various modifications could undoubtedly be made to the reamerillustrated which would not depart from the inventive concepts disclosedherein. For example, it is believed that the land 36 could be a smoothlyconvex surface and the specificshape of the radial relief 60 could bevaried from that illustrated while still obtaining the improved resultsof the present invention. The primary consideration with the formationof the radial relief 60, it is believed, is that it be dimensioned so asto not contact the bore or work surface during reamer operation.Further, while it is preferred that the tool 10 include pilot section 12to insure concentricity with the bore, the finish reaming 14. The pilotsection 24 could be dispensed with without departing from the inventiveconcepts disclosed herein. It is expressly intended, therefore, that theabove description should be considered as that of the preferredembodiment. The true spirit and scope of the present invention may bedetermined by reference to the appended claims.

The embodiments of the invention in which anexclusive property orprivilege is claimed are defined as follows:
 1. A finish reamer adaptedto finish ream a hard material, said reamer comprising:a member having aback tapered body section, said body section having a plurality offlutes, said flutes defining a plurality of cutting blades, each cuttingblade having an axially extending radial relief formed therein fordissipating heat during reamer operation, said relief extending along aportion only of said cutting blade and each of said cutting bladesincluding a pilot and surface finish portion rearwardly of each of saidradial reliefs.
 2. A finish reamer as defined by claim 1 wherein each ofsaid cutting blades includes a cutting edge and a land, said radialrelief extending transversely across the entire width of said land.
 3. Afinish reamer as defined by claim 2 wherein said radial relief includessmoothly curved forward and rearward ends and a generally flat centralportion.
 4. A finish reamer as defined by claim 3 wherein said land ofeach of said cutting blades includes a margin and a heel, said heelpositioned at an angle of relief relative to said margin.
 5. A finishreamer as defined by claim 3 wherein said cutting blades each have arake angle of approximately 2 degrees.
 6. A finish reamer as defined byclaim 5 wherein each of said lands includes a narrow margin having anedge in common with said cutting edge and a heel, said heel beingorientated at a relief angle to said margin.
 7. A finish reamer isdefined by claim 6 wherein the width of said margin is within the rangeof 27.5 percent to 40 percent of the overall width of said land.
 8. Afinish reamer adapted to finish ream a hard material, said reamercomprising:a member having a body section, said body section having aplurality of flutes, said flutes defining a plurality of cutting blades,each cutting blade having an axially extending radial relief formedtherein for dissipating heat during reamer operation, said reliefextending along a portion only of said cutting blade, each of saidcutting blades including a cutting edge and a land, said radial reliefextending transversely across the entire width of said land, said radialrelief including smoothly curved forward and rearward ends, said cuttingblades each having a rake angle of approximately 2 degrees, each of saidlands including a narrow margin having an edge in common with saidcutting edge and a heel, said heel being orientated at a relief angle tosaid margin, the width of said margin being within the range of 27.5percent to 40 percent of the overall width of said land, and said reamerincluding a pilot section, said pilot section including a cylindricalportion and a fluted tapered portion.
 9. A finish reamer as defined byclaim 8 wherein said finish reamer member body section is back taperedto prevent binding during use and said radial reliefs terminate alongsaid cutting blades rearwardly of the point of maximum diameter of saidbody section.
 10. A finish reamer as defined by claim 9 wherein theratio of the length of said radial relief along said cutting blade tothe longitudinal dimension of said body portion is approximately 0.267.11. A finish reamer as defined by claim 10 wherein said fluted taperedportion of said pilot section is separated from said body section by achamfer.
 12. A finish reamer as defined by claim 11 wherein said chamferhas a chamfer angle of approximately 30 degrees and a chamfer reliefangle of approximately 12 degrees.
 13. A finish reamer as defined byclaim 12 wherein said flutes of said tapered portion of said pilotsection define cutting blades, each blade of said pilot section having afull circular land.
 14. A finish reamer for finishing a bore, saidreamer comprising:a body section having a back tapered portion andhaving formed therein a plurality of spiral flutes, said flutes defininga plurality of cutting blades each having a rake face, a cutting edge,and a land, said land including a radial relief extending along the landa distance greater than the width of said land and terminating withinthe back tapered portion of the body section, said relief openingtransversely through the rake face of said blade, each of said cuttingblades including a pilot and surface finish portion rearwardly of eachof said radial reliefs.
 15. A finish reamer for finishing a bore, saidreamer comprising:a back tapered body section having formed therein aplurality of spiral flutes, said flutes defining a plurality of cuttingblades each having a rake face, a cutting edge, and a land, said landincluding a radial relief extending along the land a distance greaterthan the width of said land, said relief opening transversely throughthe rake face of said blade and said radial relief including smoothlyrounded leading and trailing edges and a generally flat central section,said flat section being below the land a predetermined depth, each ofsaid cutting blades including a pilot and surface finish portionrearwardly of each of said radial reliefs.
 16. A finish reamer asdefined by claim 15 wherein said body section has a maximum diameterforward of said radial relief.
 17. A finish reamer as defined by claim16 wherein said reamer further includes a pilot section separated fromsaid body section by a chamfer and a shank section joined to said bodysection.
 18. A finish reamer as defined by claim 17 wherein said pilotsection includes flutes defining cutting blades which are a continuationof the flutes of said body section.
 19. A finish reamer as defined byclaim 18 wherein the cutting blades of said body section each include aland having a margin and a heel, said heel having a surface angled at arelief angle with respect to said margin.
 20. A finish reamer as definedby claim 19 wherein the cutting blades of said pilot section eachinclude a full circular non-reliefed land.
 21. A finish reamer asdefined by claim 20 wherein said body section includes at least sixflutes, said rake face of each blade of said body section having a rakeangle of approximately 2 degrees, said relief angle being approximately10 degrees and each of said chamfers has a chamfer relief angle ofapproximately 12 degrees.
 22. A finish reamer as defined by claim 21wherein said radial relief of each of said blades has a length alongsaid blade which is approximately 26.7 percent of the overalllongitudinal length of said body section, and said blades extend thefull longitudinal length of said body section.
 23. A finish reamer asdefined by claim 22 wherein said cutting blade includes a portionbetween said chamfer and said radial relief having a length dimension ofapproximately 75 percent of the length dimension of said radial relief.24. A finish reamer as defined by claim 23 wherein the ratio of thedepth of said radial relief to the length of said radial relief isapproximately 0.014.
 25. A method of rebuilding valve guides comprisingthe steps of:positioning a tubular hard material insert within a valveguide; providing a finish reamer having a back tapered, fluted bodysection, said body section defining spiral cutting blades each having aleading edge, a rake face, a land, a trailing surface and a cuttingedge, each of said cutting blades further defining a radial reliefopening along the cutting edge and through the rake face and beginningat a point spaced from the leading edge of said blade and wherein eachof said cutting blades further includes a pilot and surface finishportion rearwardly of each of said radial reliefs; positioning saidfinish reamer within said tubular insert; and rotating said finishreamer to finish ream said insert to a predetermined inner diameter. 26.The method as defined by claim 25 wherein said finish reamer furtherincludes a pilot section forward of said back tapered fluted bodysection, said sections being separated by a chamfer and said insert isfabricated from phosphor bronze.
 27. The method as defined by claim 25wherein said radial relief defined by each of said blades have a lengthalong the cutting blade greater than the width of said land.
 28. Themethod as defined by claim 27 wherein the length of said radial reliefis approximately 26.7 percent of the overall length of said bodysection.